1. The Field of the Invention
The present invention relates to fluid handling. Specifically, the present invention relates to manually operated hydraulic syringes and methods of manufacture.
2. Prior State of the Art
Syringes are widely used to inject, dispense and extract fluids in a controlled fashion. Conventional syringes generally consist of a syringe body having a cylindrical chamber in which a piston is forced to slide. The chamber has an orifice in the end opposite the piston such that if the piston is pushed towards the orifice, fluid is ejected from the chamber into or onto a target. If the piston is forced away from the orifice, fluid at the orifice is vacuumed into the chamber.
As apparent, a source of force is needed to operate a syringe. A non-human driving mechanism, such as an electrical motor, provides this force in automated syringes. Many syringes, however, operate under the manual force of a user. Although typically less sophisticated than automated syringes, manual syringes are widely used because they are inexpensive, easily maneuverable, disposable, and do not require complex and bulky driving mechanisms.
One often encountered use of syringes is in dispensing high viscosity fluids. For example, in dentistry, high viscosity fluids such as uncured dental filling materials are often dispensed onto small targets such as a pre-drilled tooth cavity. Dispensing high viscosity fluids, however, requires the user to exert a relatively high force on the manual syringe. This required exertion can produce undesired stress and fatigue on the user. Furthermore, dispensing high viscosity fluids can be more difficult to control. For example, because of the high exertion force required to dispense high viscosity materials, it can be difficult to dispense small controlled amounts or to dispense the material at a constant or desired flow rate. The high exertion force can also result in the operator""s hand becoming shaky or unstable. Such shaking and lack of control can result in the fluid missing the target.
In one approach to overcome some of the above problems, devices such as caulking type guns have been used to dispense high viscosity fluids. Caulking type guns have a levered handle which produces a mechanical advantage. Such devices, however, are large and cumbersome relative to conventional syringes. Furthermore, some caulking type guns operate on a ratcheting system which makes it difficult to dispense in a smooth, continuous manner. Finally, since caulking type guns have a handle that orthogonally projects from the barrel, caulking type guns are limited in their use and maneuverability
Therefore, an easily maneuverable apparatus and method are desired for the controlled manual dispensing of high viscosity fluids.
Accordingly, it is an object of the present invention to provide apparatus for dispensing fluids and particularly high viscosity fluids.
Another object of the present invention is to provide apparatus as above for dispensing high viscosity fluids in a controlled manner requiring minimal exertion and stress by the user.
Finally, another object of the present invention is to provide apparatus as above which produce a magnification of an applied force so that only a minimal applied force is required to dispense high viscosity fluids.
To achieve the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a manually operated hydraulic syringe is provided. The hydraulic syringe includes a syringe barrel having an exterior surface and an interior surface. A syringe grip outwardly projects from the exterior surface of the syringe barrel. The interior surface of the syringe barrel bounds a first chamber having a first transverse cross-sectional area and a second chamber having a second transverse cross-sectional area. The first chamber is in fluid communication with the second chamber. Furthermore, the transverse cross-sectional area of the second chamber is greater than the transverse cross-sectional area of the first chamber.
A first plunger has a distal end slidably disposed within the first chamber and an opposing proximate end having a handle positioned thereat. A second plunger is slidably disposed within the second chamber. Sealed in substantial isolation within the syringe barrel is a hydraulic fluid, such as water or oil. In this configuration, manual advancement of the first plunger within the first chamber pressurizes the hydraulic fluid which in turn advances the second plunger within the second chamber.
Removably coupled to the distal end of the syringe barrel is a nozzle in which a dispensing material, such as a high viscosity fluid, is selectively disposed. In one embodiment, the nozzle comprises a disposable cartridge. Advancement of the second plunger causes a portion of the second plunger to push against the dispensing material which is then dispensed out of the attached nozzle.
One of the unique features of the present invention is that the transverse cross-sectional area of the second chamber and corresponding second plunger are greater than the transverse cross-sectional area of the first chamber and corresponding first plunger. As such, when a manual first force is applied to the first plunger so that the first plunger is advanced at a first speed, a hydraulic advantage is produced through the hydraulic fluid so that a second force greater than the first force is applied to the second plunger and the second plunger advances at a second speed that is slower than the first speed. In turn, this magnified or increased second force is applied through the second plunger to the high viscosity fluid for dispensing.
In an alternative embodiment, the barrel of the hydraulic syringe comprises a single chamber having a substantially uniform transverse cross sectional area along its length. Sealed within the chamber is a hydraulic fluid. A first plunger is coupled with the first end of the barrel so as to selectively advance within the chamber thereof. A second plunger is slidably disposed within the second end of the barrel. The first plunger has a transverse cross sectional area that is smaller than the transverse cross sectional area of the second plunger. As a result, the same hydraulic advantage is achieved. That is, as the first plunger is advanced within the chamber under a first force at a first speed, the hydraulic fluid is pressurized. In turn, the pressurized hydraulic fluid pushes against the second plunger. As a result of the second plunger having a larger surface area of displacement, the second plunger moves forward with a second force that is greater than the first force and at a second speed that is slower than the first speed.
In each of the above embodiments, as a result of the magnification of force, minimal manual force is required to be applied by the user of the hydraulic syringe to effectively dispense high viscosity fluids in a controlled mainer. Furthermore, since minimal force and thus minimal exertion is required by the user, fatigue and shaking by the user is also minimized. Finally, since the hydraulic syringe has a configuration similar to a conventional syringe, the hydraulic syringe is convenient and easily maneuvered by the user. That is, rotation of the wrist facilitates quick and easy placement for most delivery angles.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.